With the rapid development of semiconductor manufacturing technology, semiconductor devices have been developed toward high device density. As basic semiconductor devices, transistors have been widely used. With the continuous increase of the device density, the critical dimension of the gate structures of transistors has become smaller and smaller. However, reducing the critical dimension of the gate structures often causes the transistors to have a short channel effect. Thus, leakage current is generated; and the performance of the semiconductor device is affected.
A transistor usually includes a semiconductor substrate; a gate dielectric layer formed on the surface of the semiconductor substrate; a gate electrode layer formed on the gate dielectric layer; sidewall spacers formed on the semiconductor substrate and covering the side surfaces of the gate dielectric layer and the gate electrode layer; and source and drain regions formed in the semiconductor substrate at both sides of the sidewall spacers.
When the technical node is further reduced, the short channel effect of the transistor has become more intense; and the control ability of the gate structure to the channel region has become weaker and weaker. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.